My MIL makes it whenever there is a need to do instant Neivedhyam. Most of the time, she will do some prayers or the other and as an offerring prepare this in a jiffy.

Cooked Rice - 1 cup

Sugar - 1/2 cup

or 

Jaggery - 1/2 cup

Milk - 1 cup

Cardamom powder - 1 pinch

Cashew Nuts - 4

Ghee - 2 tbsp

Mash the cooked rice with the back of a laddle. Heat milk and when hot add the mashed rice, sugar or jaggery and keep stirring. Remove from flame. Add cardamom powder. Fry cashewnuts in ghee and add it to the payasam.

This can be done very easily in about 10 mins.